Immediate disarm after arm

So I decided I need to rebuild my very first quad that I built about 5 years ago with an entirely new frame and a shiny new PixHawk4.

Long story short, the PixHawk is happy, good gps, compass, barometer, controller calibration, and I can arm it without a problem, but… Within a second of arming, it disarms itself without any messages whatsoever. I have tried disabling all arming checks, no change. Also, I can do the motor tests in FlightPlanner and the motors spin up without issue, so the ESC’s are calibrating and arming.

Any ideas why it would disarm automatically like that?

This monday i have the same problem that you !!
Have you find the solucion ?
Because i don’t ;-(


I did a full reset, re-flashed the firmware, and then reinstalled everything again, and it worked. So can’t really say which step of that process fixed it.

Good luck!